Sole structure for article of footwear

ABSTRACT

An article of footwear includes an upper and a sole structure coupled with the upper. The sole structure includes a midsole that is coupled to the upper along an upper surface of the midsole and to an outsole along a lower surface that is opposite the upper surface. Both the upper surface and the lower surface are curved along a width of the sole structure to curve away from the upper and toward the outsole within a forefoot region, thus forming a rounded surface that extends throughout the forefoot region. A stiffening member is coupled to the midsole and extends from a heel end toward a toe end. The stiffening member includes a base disposed within at least a midfoot region and a plurality of tines that extend into the forefoot region from the base.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application claims the benefit of U.S. Provisional Patent Application 63/278,280, filed on Nov. 11, 2021, the entire contents of which is hereby incorporated by reference, for any and all purposes.

REFERENCE REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable

SEQUENCE LISTING

Not applicable

BACKGROUND 1. Field of the Disclosure

The present disclosure relates generally to a sole structure for an article of footwear with a rounded (e.g., hemispherical, ellipsoidal, or otherwise convex) forefoot region to provide improved traction while a user is moving along an angled surface, or to minimize pronation and supination while a user is turning so as to ensure that the user's ankle is aligned over the respective foot. The sole structure includes a midsole having a lower surface that is rounded along a length or a width of the sole structure, and an outsole. In addition, the sole structure can include a stiffening element that is coupled to the midsole. The stiffening element generally extends along a length of the sole structure, e.g., from a heel end to a toe end, and includes tines extending along the forefoot region. The tines can be tuned to provide the forefoot region with differing levels of support and stability to reduce supination or pronation.

2. Description of the Background

Many conventional shoes or other articles of footwear generally comprise an upper and a sole attached to a lower end of the upper. Conventional shoes further include an internal space, i.e., a void or cavity, which is created by interior surfaces of the upper and sole that receives a foot of a user before securing the shoe to the foot. The upper generally extends upward from the sole and defines an interior cavity that completely or partially encases a foot. In most cases, the upper extends over instep and toe regions of the foot, and across medial and lateral sides thereof. Many articles of footwear may also include a tongue that extends across the instep region to bridge a gap between edges of medial and lateral sides of the upper, which define an opening into the cavity. The tongue can be disposed below a lacing or other closure system and between medial and lateral sides of the upper, to allow for adjustment of shoe tightness. The tongue may be manipulable by a user to permit entry or exit of a foot from the internal space or cavity. In addition, the lacing system may allow a user to adjust certain dimensions of the upper or the sole, thereby allowing the upper to accommodate a wide variety of foot types having varying sizes and shapes.

The upper may comprise a wide variety of materials, which may be chosen based on one or more intended uses of the shoe. The upper may also include portions comprising varying materials specific to a particular area of the upper. For example, added stability may be desirable at a front of the upper or adjacent a heel region so as to provide a higher degree of resistance or rigidity. In contrast, other portions of a shoe may include a soft woven textile to provide an area with stretch-resistance, flexibility, air-permeability, or moisture-wicking properties.

The sole is attached to a lower surface or boundary of the upper and is positioned between the upper and the ground. As a result, the sole typically provides stability and cushioning to the user when the shoe is being worn. In some instances, the sole may include multiple components, such as an outsole, a midsole, and an insole. The outsole may provide traction to a bottom surface of the sole, and the midsole may be attached to an inner surface of the outsole and may provide cushioning or added stability to the sole. For example, a sole may include a particular material or be configured in a particular shape that may increase stability at one or more desired locations along the sole, or that may reduce stress or impact energy on the foot or leg when a user is running, walking, or engaged in another activity.

Sole assemblies generally extend between a ground surface and the upper. In some examples, the sole assembly includes an outsole that provides abrasion-resistance and traction with the ground surface. The outsole may be formed from rubber or other materials that impart durability and wear-resistance, as well as enhancing traction with the ground surface.

However, while many currently available shoes have varying features related to the above-noted properties, many shoes, including athletic shoes and hiking shoes, have sole structures with bottom surfaces that are generally flat along a width of the sole structure, e.g., a direction extending between lateral and medial sides of the sole structure, which can require kinematic modulations from a user in order to maintain appropriate contact with the ground when on uneven surfaces or while moving along a curve. Put another way, a user must intentionally pronate or supinate so as to maintain contact between the bottom surface of the sole structure and the ground. Pronation and supination, especially when under increased loading due to strenuous activities, such as running and hiking, can lead to injuries. In addition, pronation and supination can reduce efficient power transfer between the user and the ground, thereby decreasing performance.

Therefore, articles of footwear having features that aid in stability and traction are desired. These and other deficiencies with the prior art are outlined in the following disclosure.

SUMMARY

A number of advantages of the articles of footwear described herein will be apparent to those having ordinary skill in the art. For example, an article of footwear can include a midsole with a rounded forefoot portion to allow a foot of a user to maintain a neutral position while moving along uneven ground or along a curve, and may also include a stiffening member to tune the stiffness and support provided by the midsole.

According to one aspect, a sole structure for an article of footwear having an upper can include a midsole that can be coupled to the upper along an upper surface of the midsole and to an outsole along a lower surface that is opposite the upper surface. Both the upper surface and the lower surface can be curved along a width of the sole structure to curve away from the upper and toward the outsole within a forefoot region. The sole structure can further include a stiffening member that can be coupled to the midsole. The stiffening member can extend from a heel end toward a toe end, and can include a base disposed within at least a midfoot region and a plurality of tines extending into the forefoot region from the base.

In some embodiments, along the width of the sole structure, the upper surface can define a first curvature and the lower surface can define a second curvature. The first curvature can be different from the second curvature so that the midsole has a crescent-like cross-sectional shape taken perpendicular to a longitudinal axis of the sole structure. In some cases, the first curvature can define a first radius of curvature and the second curvature can define a second radius of curvature, which can be smaller than the first radius of curvature.

In some embodiments, the lower surface can be curved to have an ellipsoidal shape in the forefoot region, or more specifically, a hemispherical shape. In some cases, a plurality of ground engaging elements can extend radially outward from the lower surface in the forefoot region.

In some embodiments, the midsole can include a first midsole portion that can be disposed in the forefoot region and a second midsole portion that can be disposed in a heel region of the sole structure. The first midsole portion and the second midsole portion can be spaced apart from one another by a gap in the midfoot region. The stiffening member can bridge the gap between the first midsole portion and the second midsole portion, such that the first midsole portion and the second midsole portion can be in a fixed spaced relationship.

In some embodiments, the plurality of tines can include a first tine extending along a lateral side of the sole structure and a second tine extending along a medial side of the sole structure. In some cases, a third tine can be positioned between the first tine and the second tine. The third tine can extend along a longitudinal axis of the sole structure. In some cases, the base of the stiffening member can extend into a heel region of the sole structure.

In some embodiments, the plurality of tines can be disposed within the midsole in the forefoot region. More specifically, the midsole can include an upper midsole layer defining the upper surface and a lower midsole layer defining the lower surface, and the plurality of tines can be disposed between the upper midsole layer and the lower midsole layer. In some cases, the base of the stiffening member can extend along the upper surface in the midfoot region.

According to another aspect, a sole structure for an article of footwear having an upper can include a midsole and a stiffening member. The midsole can define an upper surface configured to couple to the upper and a lower surface opposite the upper surface. The lower surface can be curved in a forefoot region of the sole structure so that the lower surface has an ellipsoidal shape. The stiffening member can include a plurality of tines that extend from a base. The plurality of tines can extend in a heel-to-toe direction within the forefoot region and can include at least a first tine and a second tine. The first tine can extend along a first curvature along a lateral side of the midsole to provide the lateral side of the midsole with a first stiffness and the second tine can extend along a second curvature along a medial side of the midsole to provide the medial side of the midsole with a second stiffness.

In some embodiments, the midsole can have a crescent-like cross-sectional shape taken perpendicular to a longitudinal axis of the sole structure. Accordingly, the midsole can be thickest proximate the longitudinal axis and can gradually thin moving outward toward each of a medial side and a lateral side of the sole structure.

In some embodiments, the sole structure can further include an outsole that is coupled to the lower surface of the midsole to provide a ground engaging surface. The outsole can conform with the shape of the lower surface, such that the ground engaging surface also conforms with the shape of the lower surface.

According to yet another aspect, a sole structure for an article of footwear having an upper can include a midsole and a stiffening member. The midsole can be configured to couple to the upper along an upper surface of the midsole and to an outsole along a lower surface that is opposite the upper surface. The lower surface can be curved along both of a width and a length of the sole structure to form a continuously rounded and convex surface that extends throughout a forefoot region of the sole structure. The stiffening member can be coupled to the midsole and can include a plurality of tines that extend from a base. The plurality of tines can extend in a heel-to-toe direction within the forefoot region and can include at least a first tine and a second tine. The first tine can extend along a first curvature along a lateral side of the midsole to provide the lateral side of the midsole with a first stiffness and the second tine extending along a second curvature along a medial side of the midsole to provide the medial side of the midsole with a second stiffness.

Other aspects of the articles of footwear described herein, including features and advantages thereof, will become apparent to one of ordinary skill in the art upon examination of the figures and detailed description herein. Therefore, all such aspects of the articles of footwear are intended to be included in the detailed description and this summary.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top, front, and lateral perspective view of a sole structure for an article of footwear according to aspects of the disclosure;

FIG. 2 is a lateral side elevational view of the sole structure of FIG. 1 ;

FIG. 3 is a medial side elevational view of the sole structure of FIG. 1 ;

FIG. 4 is a top plan view of the sole structure of FIG. 1 ;

FIG. 5 is a bottom plan view of the sole structure of FIG. 1 ;

FIG. 6 is a cross sectional view of the sole structure of FIG. 1 taken along line VI-VI in FIG. 3 ;

FIG. 7 is a top, front, and lateral perspective view of another sole structure for an article of footwear according to aspects of the disclosure;

FIG. 8 is a cross sectional view of the sole structure of FIG. 7 taken along line VIII-VIII;

FIG. 9 is a top, front, and lateral perspective view of another sole structure for an article of footwear according to aspects of the disclosure;

FIG. 10 is a cross sectional view of the sole structure of FIG. 9 taken along line X-X;

FIG. 11 is a top schematic view of the sole structure of FIG. 9 showing lines of curvature of a midsole;

FIG. 12 is a top view of the sole structure of FIG. 9 , with a stiffening member shown in phantom; and

FIG. 13 is lateral exploded view of another sole structure for an article of footwear according to aspects of the disclosure.

DETAILED DESCRIPTION OF THE DRAWINGS

The following discussion and accompanying figures disclose various embodiments or configurations of a shoe having an upper and a sole structure. Although embodiments are disclosed with reference to a sports shoe, such as a running shoe, tennis shoe, basketball shoe, etc., concepts associated with embodiments of the shoe may be applied to a wide range of footwear and footwear styles, including basketball shoes, cross-training shoes, football shoes, golf shoes, hiking shoes, hiking boots, ski and snowboard boots, soccer shoes and cleats, walking shoes, and track cleats, for example. Concepts of the shoe may also be applied to articles of footwear that are considered non-athletic, including dress shoes, sandals, loafers, slippers, and heels.

The term “about,” as used herein, refers to variations in the numerical quantity that may occur, for example, through typical measuring and manufacturing procedures used for articles of footwear or other articles of manufacture that may include embodiments of the disclosure herein; through inadvertent error in these procedures; through differences in the manufacture, source, or purity of the ingredients used to make the compositions or mixtures or carry out the methods; and the like. Throughout the disclosure, the terms “about” and “approximately” refer to a range of values ±5% of the numeric value that the term precedes.

Also as used herein, unless otherwise limited or defined, “or” indicates a non- exclusive list of components or operations that can be present in any variety of combinations, rather than an exclusive list of components that can be present only as alternatives to each other. For example, a list of “A, B, or C” indicates options of: A; B; C; A and B; A and C; B and C; and A, B, and C. Correspondingly, the term “or” as used herein is intended to indicate exclusive alternatives only when preceded by terms of exclusivity, such as “only one of,” or “exactly one of.” For example, a list of “only one of A, B, or C” indicates options of: A, but not B and C; B, but not A and C; and C, but not A and B. In contrast, a list preceded by “one or more” (and variations thereon) and including “or” to separate listed elements indicates options of one or more of any or all of the listed elements. For example, the phrases “one or more of A, B, or C” and “at least one of A, B, or C” indicate options of: one or more A; one or more B; one or more C; one or more A and one or more B; one or more B and one or more C; one or more A and one or more C; and one or more A, one or more B, and one or more C. Similarly, a list preceded by “a plurality of” (and variations thereon) and including “or” to separate listed elements indicates options of multiple instances of any or all of the listed elements. For example, the phrases “a plurality of A, B, or C” and “two or more of A, B, or C” indicate options of: one or more A and one or more B; one or more B and one or more C; one or more A and one or more C; and one or more A, one or more B, and one or more C.

Further, as used herein, unless otherwise defined or limited, directional terms are used for convenience of reference for discussion of particular figures or examples. For example, references to “downward,” or other directions, or “lower” or other positions, may be used to discuss aspects of a particular example or figure, but do not necessarily require similar orientation or geometry in all installations or configurations.

The terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers or sections. These elements, components, regions, layers or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example configurations.

The present disclosure relates to an article of footwear having a sole structure attached to the upper. The sole structure includes a midsole that may be attached to the upper, and an outsole attached below the midsole to define a bottom of the article of footwear. In some embodiments, the midsole and the outsole may be a unitary body made from a foam or a rubber material, which cushion the user's foot as it impacts the ground and gives the user traction. In other embodiments, the midsole and the outsole can be different components that can be co-molded or adhered together by a glue or other adhesive. For example, the midsole may be made of a foam material (e.g., EVA) to provide cushioning, and the outsole may be a rubber material to increase traction and durability, among other types of materials. Moreover, the midsole can be a multi-density midsole with two or more layers having different densities to provide tuned cushioning characteristics. Both the midsole and the outsole can vary in thickness, e.g., a dimension taken normal to a bottom surface of the outsole. Additionally, one or both of the midsole and the outsole may be formed from one or more sections.

A midsole can be shaped to have a rounded bottom surface that can reduce the need for a user to provide kinematic modulations, e.g., intentional pronation or supination, to maintain contact, and therefore traction, between the outsole and the ground. For example, a midsole can define a rounded or curved midsole portion that is configured to have a crescent-like cross-section when taken perpendicular to the length of the article of footwear. That is, the midsole portion can define an upper surface that is configured to couple with an upper and a lower surface that is configured to couple with an outsole.

Both the upper surface and the lower surface can be curved along a width, e.g., a local width extending between a lateral side and a medial side, of the article of footwear to curve away from the upper and toward the outsole. In some cases, the upper surface can define a first curvature (e.g., a first radius of curvature) that is larger than a second curvature (e.g., a second radius of curvature) of the lower surface. Accordingly, the midsole has a thickness, e.g., a dimension taken normal to the lower surface between the lower surface and the upper surface, that is greatest proximate a longitudinal axis of the article of footwear and gradually becomes thinner moving outward toward each of the medial and lateral sides.

In some embodiments, a midsole can be curved in multiple directions. For example, a midsole portion of a midsole can be curved along a width of the article of footwear, as described above, and can be similarly curved along a length that is perpendicular to the width. Accordingly, the midsole can have a crescent-like cross-section taken both perpendicularly to the width and perpendicularly to the length. Put another way, a midsole can define a concave upper surface and a convex lower surface. The concave upper surface can be configured to couple with an upper so as to receive a foot of a user. The convex lower surface can be configured to couple to the outsole. Correspondingly, the outsole can be curved to follow along the lower surface of the midsole. The respective curvatures of the lower surface, e.g., a curvature along the width and a curvature along the length, can be tailored to give the lower surface a desired rounded shape, for example, an ellipsoidal, ovoid, or hemispherical shape.

Accordingly, a convex lower surface of a midsole can allow a foot of a user to remain neutral, i.e., neither pronated nor supinated, during activities. For example, when a user moves over an angled or uneven surface, e.g., while hiking or trail running, with a conventional, non-rounded sole structure, to maintain proper traction with the ground, the user must pronate or supinate to position the bottom surface of the sole structure in parallel with the ground. However, with a rounded midsole portion and a correspondingly rounded outsole, the curvature of the bottom surface of the sole structure can allow the foot of the user to remain in a neutral position by providing a portion of the bottom surface that is parallel to the ground, even with the foot in a neutral position. Similarly, if a user is running along a curve with a conventional shoe, the user will naturally lean into the curve, thereby requiring the user to supinate or pronate to place the bottom surface of the shoe in parallel with the ground. However, with a rounded midsole portion and a correspondingly rounded outsole, the curvature of the bottom surface of the sole structure inherently provides a surface that is, or is close to, parallel with the ground, thereby allowing the foot to maintain a more neutral position. Relatedly, with the foot of the user in a neutral position, a user may be able to more efficiently transfer force, i.e., energy, into the ground, thereby improving performance.

In some embodiments, a midsole can include multiple, discrete midsole portions. For example, a midsole can include a first midsole portion disposed generally throughout a forefoot region and a second midsole portion disposed generally throughout a heel region. The first midsole portion and the second midsole portion may be separated from one another by a gap extending across a local width of the article of footwear in a midfoot region. Both the first midsole portion and the second midsole portion can be rounded portions that are curved along one or both of a width and a length of the article of footwear to provide respective rounded bottom surfaces.

To provide enhanced stability, a sole structure can also include a stiffening member. For example, a sole structure can include a stiffening member that is configured to couple with an upper surface of a midsole, so as to be disposed between the midsole and an upper. Accordingly, the stiffening member can be a generally flat, curvilinear member with a curvature corresponding to a curvature of the upper surface of the midsole. The stiffening member can be a fork-like stiffening member with a plurality of tines that extend from a base, although other configurations are possible. In particular, the base can be disposed generally within a heel region and the tines can extend forward from the base and into the forefoot region, wherein each tine terminates at a respective distal end proximate a toe end. In other configurations, the stiffening member can be configured differently. For example, the base may extend throughout a heel region and into a midfoot region, and the tines may extend from the midfoot region and throughout the forefoot region, or the base may be generally disposed within a midfoot region and the tines may extend from the midfoot region into one or both of the forefoot region and the heel region.

FIGS. 1-6 depict an exemplary embodiment of an article of footwear 100 including an upper 102 (shown in phantom in FIG. 6 ) and a sole structure 104. As will be discussed in further detail below, the upper 102 is coupled with the sole structure 104 and together with the sole structure 104 defines an interior cavity 106 (see FIG. 6 ) into which a foot of a user may be inserted. The upper 102 can include an insole (not shown) positioned within the interior cavity 106, which can be in direct contact with a user's foot while the article of footwear 100 is being worn. In some embodiments, the upper 102 may also include a liner (not shown) that can increase comfort, for example, by reducing friction between the foot of the user and the upper 102, or providing moisture wicking properties. The liner may line the entire interior cavity 106 or only a portion thereof. In other embodiments, a binding (not shown) may surround the opening of the interior cavity 106 to secure the liner to the upper 102 or to provide an aesthetic element on the article of footwear 100. Furthermore, the sole structure 104 includes a midsole 112 and an outsole 114 coupled to and disposed generally below the midsole 112, which defines a bottom surface 116 of the article of footwear 100. The outsole 114 can be configured to contact the ground.

For reference, the article of footwear 100 generally defines a forefoot region 120, a midfoot region 122, and a heel region 124 (see FIGS. 1-5 ). The forefoot region 120 generally corresponds with portions of the article of footwear 100 that encase portions of the foot that include the toes, the ball of the foot, and joints connecting the metatarsals with the toes or phalanges. The midfoot region 122 is proximate and adjoining the forefoot region 120, and generally corresponds with portions of the article of footwear 100 that encase the arch of a foot, along with the bridge of a foot. The heel region 124 is proximate and adjoining the midfoot region 122 and generally corresponds with portions of the article of footwear 100 that encase rear portions of the foot, including the heel or calcaneus bone, the ankle, or the Achilles tendon.

With continued reference to FIGS. 1-5 , the article of footwear 100 also defines a lateral side 126 and a medial side 128. Further, the article of footwear 100 defines a longitudinal axis 130 that extends from a toe end 132, located at a distal end of the forefoot region 120, to a heel end 134, located at a distal end of the heel region 124 opposite the toe end 132. The longitudinal axis 130 defines a middle of the article of footwear 100 with the lateral side 126 extending from one side of the longitudinal axis 130 and the medial side 128 extending from the other. Put another way, the lateral side 126 and the medial side 128 adjoin one another along the longitudinal axis 130. In particular, the lateral side 126 corresponds to an outside portion of the article of footwear 100 and the medial side 128 corresponds to an inside portion of the article of footwear 100. As such, left and right articles of footwear have opposing lateral 126 and medial 128 sides, such that the medial sides 128 are closest to one another when a user is wearing the article of footwear 100, while the lateral sides 126 are defined as the sides that are farthest from one another while being worn.

The forefoot region 120, the midfoot region 122, the heel region 124, the medial side 128, and the lateral side 126 are intended to define boundaries or areas of the article of footwear 100, and collectively span an entire length of the article of footwear 100, from the toe end 132 to the heel end 134. It should be appreciated that aspects of the disclosure may refer to portions or elements that are coextensive with one or more of the forefoot region 120, the midfoot region 122, the heel region 124, the medial side 128, or the lateral side 126. The forefoot region 120 extends from the toe end 132 to a widest portion 136 of the article of footwear 100, i.e., a distance between the medial side 128 and the lateral side 126 of the sole structure 104. The midfoot region 122 extends from the widest portion 136 to a thinnest portion 138 of the article of footwear 100, i.e., a distance between the medial side 128 and the lateral side 126 of the sole structure 104. The heel region 124 extends from the thinnest portion 138 to the heel end 134 of the article of footwear 100.

Still referring to FIGS. 1-5 , the lateral side 126 begins where the toe end 132 intersects the longitudinal axis 130 and bows outward, i.e., away from the longitudinal axis 130, along the forefoot region 120 toward the midfoot region 122. At the widest portion 136, the lateral side 126 bows inward, i.e., toward the longitudinal axis 130, toward the thinnest portion 138, entering the midfoot region 122. Upon reaching the thinnest portion 138, the lateral side 126 bows outward and extends into the heel region 124. The lateral side 126 then bows back inward toward the heel end 134 and terminates where the heel end 134 intersects with the longitudinal axis 130. Similarly, the medial side 128 begins where the toe end 132 intersects the longitudinal axis 130 and bows outward, i.e., away from the longitudinal axis 130, along the forefoot region 120 toward the midfoot region 122. At the widest portion 136, the medial side 128 bows inward, i.e., toward the longitudinal axis 130, toward the thinnest portion 138, entering the midfoot region 122. Upon reaching the thinnest portion 138, the medial side 128 bows outward and extends into the heel region 124. The medial side 128 then bows back inward toward the heel end 134 and terminates where the heel end 134 intersects with the longitudinal axis 130.

It should be understood that numerous modifications may be apparent to those skilled in the art in view of the foregoing description, and individual components thereof, may be incorporated into numerous articles of footwear. Accordingly, aspects of the article of footwear 100 and components thereof, may be described with reference to general areas or portions of the article of footwear 100, with an understanding the boundaries of the forefoot region 120, the midfoot region 122, the heel region 124, the lateral side 126, or the medial side 128 as described herein may vary between articles of footwear. Furthermore, aspects of the article of footwear 100 and individual components thereof, may also be described with reference to exact areas or portions of the article of footwear 100 and the scope of the appended claims herein may incorporate the limitations associated with these boundaries of the forefoot region 120, the midfoot region 122, the heel region 124, the lateral side 126, or the medial side 128 discussed herein.

An upper can be configured to at least partially enclose the foot of a user and may be made from one or more materials. As illustrated in FIG. 6 , the upper 102 is disposed above and is coupled to the sole structure 104. The upper 102 can extend along the entirety of each of the medial 128 and lateral 126 sides, as well as extend over the top of the forefoot region 120 and around the heel region 124. An upper can be formed from one or more layers. For example, many conventional uppers are formed from multiple elements (e.g., textiles, polymer foam, polymer sheets, leather, and synthetic leather) that are joined through bonding or stitching at a seam. In various embodiments, a knitted component may incorporate various types of yarn that may provide different properties to an upper. In other embodiments, the upper may incorporate multiple layers of different materials, each having different properties, for example, increased breathability or moisture wicking.

A number of other features may also be coupled to or included in an upper to provide or enhance certain properties of the upper. For example, an upper can include a tongue (not shown) that may include a tongue lining or a foam pad to increase comfort. The tongue may be a separate component that is attached to the upper or it may be integrally formed with one or more layers of the upper. Additionally, an upper can also include a tensioning system (not shown) that allows a user to adjust the upper to fit a foot of a user. The tensioning system can extend through a midfoot region or a forefoot region of the upper and may be attached to the upper by an attachment structure. For example, an upper may include a plurality of holes (e.g., punch holes) or eyelets that are configured to slidably receive laces so that the user can secure, e.g., by tightening and tying the laces, the article of footwear to a foot. In other embodiments, a tensioning system may be another laceless fastening system known in the art.

The upper 102 is joined with the sole structure 104, which extends between the upper 102 and the ground. The sole structure 104 includes the midsole 112 and the outsole 114. In other embodiments, a sole structure may also include one or more other components, which may include a lasting board, a plate, or a strobel board (not shown), that are disposed between a midsole and an upper. Additionally, in some cases, a sole structure can further include a heel cup that couples with the upper in the heel region via an adhesive or stitching and provides additional support to a heel of a user. More specifically, a heel cup may be made from a rigid or semi-rigid material, for example, TPU or a composite that allows the heel cup to flex or give as needed when a user is running or engaging in other activities, but otherwise provide more rigid support to the heel of a user. In some embodiments, a heel cup can be made of a translucent or clear TPU to enhance the aesthetic appeal.

With continued reference to FIGS. 1-5 , the midsole 112 is defined as the portion of the sole structure 104 that extends between the upper and the outsole 114. That is, the midsole 112 is coupled with the upper 102 at an upper surface 140 of the midsole 112 and is coupled with the outsole 114 on a lower surface 142 of the midsole 112, opposite the upper 102. The midsole 112 can extend along the length of the sole structure 104, throughout a forefoot region 120, a midfoot region 122, and a heel region 124. Additionally, the midsole 112 extends across the width of the sole structure 104 from the lateral side 126 to the medial side 128.

The midsole 112 can act to cushion a user from the impact caused by the user's foot striking the ground. Put another way, the midsole 112 absorbs the impact resulting from a foot of a user coming into contact with the ground. To provide the desired cushion characteristics, the thickness of the midsole 112, e.g., a dimension taken along direction that is normal to the bottom surface 116, can be varied, with thicker regions providing greater cushioning and stability, and thinner regions providing lesser cushioning and greater flexibility. For example, in the illustrated embodiment, the midsole 112 is thickest within the forefoot region 120. However, other configurations are possible and a midsole can be tailored to provide cushioning in accordance with a specific purpose, such as running, trail running, soccer, or hiking.

Accordingly, the midsole 112, including any individual cushioning members that make up the midsole 112, can be made of one or more materials to provide the midsole 112 with the desired cushioning characteristics. For example, a cushioning member of a midsole may be individually constructed from a thermoplastic material, such as polyurethane (PU), for example, or an ethylene-vinyl acetate (EVA), copolymers thereof, or a similar type of material. In other embodiments, cushioning members of a midsole may be an EVA-Solid-Sponge (“ESS”) material, an EVA foam (e.g., PUMA® ProFoam Lite™, IGNITE Foam), polyurethane, polyether, an olefin block copolymer, a thermoplastic material (e.g., a thermoplastic polyurethane, a thermoplastic elastomer, a thermoplastic polyolefin, etc.), or a supercritical foam. A cushioning member may be a single polymeric material or may be a blend of materials, such as an EVA copolymer, a thermoplastic polyurethane, a polyether block amide (PEBA) copolymer, or an olefin block copolymer. One example of a PEBA material is PEBAX®.

In embodiments where a cushioning member is formed from a supercritical foaming process, the supercritical foam may comprise micropore foams or particle foams, such as a TPU, EVA, PEBAX®, or mixtures thereof, manufactured using a process that is performed within an autoclave, an injection molding apparatus, or any sufficiently heated/pressurized container that can process the mixing of a supercritical fluid (e.g., CO₂, N₂, or mixtures thereof) with a material (e.g., TPU, EVA, polyolefin elastomer, or mixtures thereof) that is preferably molten. During an exemplary process, a solution of supercritical fluid and molten material is pumped into a pressurized container, after which the pressure within the container is released, such that the molecules of the supercritical fluid rapidly convert to gas to form small pockets, e.g., pockets of nitrogen gas, within the material and cause the material to expand into a foam, which may be used as the cushioning member. In further embodiments, a first cushioning member may be formed using alternative methods known in the art, including the use of an expansion press, an injection machine, a pellet expansion process, a cold foaming process, a compression molding technique, die cutting, or any combination thereof. For example, a first cushioning member may be formed using a process that involves an initial foaming step in which supercritical gas is used to foam a material and then compression molded or die cut to a particular shape.

In addition, a midsole can be configured to have a rounded lower surface, and accordingly, a rounded bottom surface of a sole structure. For example, the midsole 112 defines two rounded midsole portions, namely, a forefoot or first midsole portion 144 disposed within and throughout the forefoot region 120, i.e., a forefoot portion of the midsole 112, and a heel or second midsole portion 146 disposed within and throughout the heel region 124, i.e., a heel portion of the midsole 112. With particular reference to FIG. 6 , the first midsole portion 144 defines a first upper surface portion 150 of the upper surface 140 and a first lower surface portion 152 of the lower surface 142, both of which are configured as curved surfaces, e.g., to have an at least partially ellipsoidal, or more specifically, hemispherical, curvature perpendicular to the longitudinal axis 130 or along the longitudinal axis.

More specifically, each of the first upper and lower surface portions 150, 152 are curved along a width of the first midsole portion 144 so that they curve downward, i.e., away from the upper 102 and toward the ground. Accordingly, the first upper surface portion 150 can define a first curvature along its width (e.g., a local width) and the first lower surface portion 152 can define a second curvature along its width (e.g., a local width), which may or may not be a constant curvature (e.g., a radius of curvature). For example, as illustrated in FIG. 6 , the upper surface 150 defines constant curvature with a first radius of curvature 151 and the lower surface 152 defines constant curvature with a second radius of curvature 153. A center point for each of the first radius of curvature 151 and the second radius of curvature 153 can be approximately centered between the lateral side 126 and the medial side 128, so as to be approximately vertically aligned with the longitudinal axis 130. In some cases, the first and second curvatures may vary along the length of the first midsole portion 144, i.e., a length of the article of footwear 100.

As illustrated, the first curvature can be greater than the second curvature to provide the first midsole portion 144 with a crescent-like cross-section along its width, although, other configurations are possible, for example, a semi-elliptical or semi-circular shape. More specifically, the first upper surface portion 150 and the first lower surface portion 152 can be curved so that the first midsole portion 144 is thickest along the longitudinal axis 130 and gradually becomes thinned moving outward toward each of the medial side 128 and the lateral side 126. Relatedly, the curvatures of each of the first upper surface portion 150 and the first lower surface portion 152 can be tuned to achieve desired performance characteristics. For example, the first upper surface portion 150 and the first lower surface portion 152 can be curved so that a thickest portion, taken between the upper 102 and the first outsole portion 162, is disposed closer to the medial side 128 than to the lateral side 126, or vice versa, or along the longitudinal axis 130. Moreover, while only a single article of footwear is depicted, each article of footwear in a pair can have different curvatures to provide improved performance in specific scenarios, for example, running on a track. For example, a right shoe may have curvatures that are arranged to have a thickest portion offset to a lateral side and a corresponding left shoe may have curvatures that are arranged to have a thickest portion offset to a medial side.

Additionally, the first midsole portion 144 can be similarly curved along the longitudinal axis. Thus, the first midsole portion 144 can have a crescent-like shape along its length from the toe end to the opposite end, e.g., at the midfoot region 122. Correspondingly, the first midsole portion 144 can have a thickest portion proximate the widest portion 136 of the sole structure 104, and may gradually thin moving forward to the toe end 132 and moving rearward to the heel end 134. The curvatures of the first upper surface portion 150 and the first lower surface portion 152 can be different, such that the thickest portion may be offset rearward or forward of the widest portion 136. The front-to-back position of the thickest portion can be different for each of a left and right shoe, or it may be the same, as may provide improved performance in specific scenarios.

Correspondingly, due to the curvature of the first lower surface portion 152 along each of the width and the length of the first midsole portion 144, the entirety of the first lower surface portion 152 can be convex in both directions, such that the lower surface of the forefoot region 120 can be entirely convex. Put another way, the forefoot region 122 can define a single, continuously rounded surface, which can be, in some cases, ellipsoidal or hemispherical in nature.

Furthermore, a midsole can have a lower surface that is rounded in multiple directions. For example, with specific reference to FIGS. 1-3 , the first midsole portion 144 can also be rounded along a length of the article of footwear 100, e.g., along the longitudinal axis 130. More specifically, each of the first upper surface portion 150 and the first lower surface portion 152 can be curved downward toward the outsole 114 so that the first upper surface portion 150 defines a third curvature along its length (e.g., a local length) and the first lower surface portion 152 defines a fourth curvature along its length (e.g., a local length). Each of the third and fourth curvatures can vary along the width of the first midsole portion 144. Accordingly, the first upper surface portion 150 can be a concave surface while the first lower surface portion 152 can be a convex surface. That is, the first upper surface portion 150 is concave relative to a first primary axis 154 that extends normal to the first upper surface portion 150, e.g., so that the upper surface 150 curves to extend generally along the direction of the extension of the axis 154 and away from the lower surface 152. Likewise, the first lower surface portion 152 is convex relative to a second primary axis 156 that extends normal to the first lower surface portion 152, e.g., so that the lower surface 154 curves to extend generally opposite the direction of the extension of the axis 156 and toward the upper surface 150. Correspondingly, the first lower surface portion 152 can be entirely convex in the forefoot region 120, such that the first lower surface portion 152 is continuously curved from the lateral side 126 to the medial side 128 and from the toe end 132 to the midfoot region 122.

By providing a rounded lower surface, a midsole can allow a foot of a user to maintain a more neutral position when traveling along uneven ground or along a curve. In particular, the curved nature of the first lower surface portion 152 of the first midsole portion 144, allows at least a portion of the bottom surface 116 of the sole structure 104, e.g., the outsole 114, to be parallel with the ground when the ground is angled, i.e., not horizontal, or when it is advantageous for a user to angle their body relative to the ground, such as when running along a curved track. Accordingly, a user may not have to actively pronate or supinate their foot to maintain sufficient contact, e.g., traction, between the bottom surface 116 of the sole structure 104 and the ground. Thus, the user's foot can maintain a more neutral position that can reduce the possibly of injury, e.g., rolling an ankle, and can also provide for more efficient energy transfer to the ground.

In some embodiments, the second midsole portion 146 can be rounded in a manner that is similar to the first midsole portion 144, and can define a second upper surface portion 158 and a second lower surface portion 160. However, the second midsole portion 146 may also be configured differently. Relatedly, since the midsole 112 is comprising of the first midsole portion 144 and the second midsole portion 146, the outsole 114 can be similarly configured to have a first outsole portion 162 coupled to the first midsole portion 144 and a second outsole portion 164 coupled to the second midsole portion 146. Each of the first outsole portion 162 and the second outsole portion 164 can be configured to follow the contours of the first midsole portion 144 and the second midsole portion 146, respectively.

To provide additional support, a sole structure can further include a stiffening member. A stiffening member can be configured to provide tuned lateral stiffness, e.g., along a width, or tuned longitudinal stiffness, e.g., along a length, stiffness. That is, a stiffening member can be shaped to provide desired stiffening characteristics, and can also be made from one or more materials, such as, plastics, metals, or composite material, e.g., carbon fiber. Still referring to FIGS. 1-6 , the sole structure 104 can include a stiffening member 170, which can be configured as a substantially flat and curvilinear member that is coupled to the upper surface 140 of the midsole 112, e.g., between the midsole 112 and the upper 102. That is, the stiffening member 170 can be shaped to follow along the respective curvatures of each of the first upper surface portion 150 and the second upper surface portion 158. In other embodiments, a stiffening member may be disposed within a corresponding recess formed along an upper surface of a midsole, or may be disposed entirely within a midsole.

A stiffening member can be shaped to tune the stiffness and support characteristics of a sole structure. For example, as illustrated, the stiffening member 170 can be configured as a fork-like stiffening member having a plurality of tines 172 that extend from a base 174; however, other configurations are possible. The base 174 is disposed within heel region 124 and can extend partially or entirely into the midfoot region 122. The tines 172 extend forward from the base 174 in a heel-to-toe direction, i.e., from the heel end 134 to the toe end 132, to extend through the forefoot region 120, where the tines 172 each terminate at respective distal ends proximate the toe end 132. In the illustrated embodiment, the distal ends of the tines 172 can wrap upwardly at the toe end 132 to couple with the upper 102; however, other embodiments can be configured differently.

Any of the quantity, location, size, and spacing of the tines can be varied to tune the stiffness characteristics of the sole structure. For example, in the illustrated embodiment, the plurality of tines 172 includes three similarly-sized tines, e.g., with similar lengths, widths, and thicknesses, namely, a lateral or first tine 176 extending along the lateral side 126 of the midsole 112, a medial or second tine 178 extending along the medial side 128, and a central or third tine 180 extending generally along the longitudinal axis 130. Each of the first tine 176 and the second tine 178 are curved to follow a respective contour of the lateral side 126 and the medial side 128 of the midsole 112, and are approximately evenly spaced apart from the third tine 180, which is substantially straight. In this way, each of the tines 172 extends along a respective curvature of the midsole 112, e.g., the first upper surface portion 150 of the first midsole portion 144.

Accordingly, the tines 172 can provide the sole structure 104 with similar stiffness along the lateral and medial sides 126, 128. In other embodiments, this may not be the case, and various parameters of the tines 172 can be modified to give the midsole 112 varied stiffness characteristics. For example, the tines can increase in thickness moving from a lateral side to a medial side to provide a flexible lateral side and more supportive medial side, or vice versa.

Turning now to FIGS. 7 and 8 , another exemplary embodiment of an article of footwear 200 is illustrated. The article of footwear 200 is similar to the article of footwear 100, in accordance with the description above, with like reference numerals referring to like features. In particular, the article of footwear 200 includes an upper 202 (shown in phantom in FIG. 8 ) that is coupled to and disposed above a sole structure 204, which extends between the upper 202 and the ground throughout a forefoot region 220, a midfoot region 222, and a heel region 224. That is, the article of footwear 200 has a width extending between a lateral side 226 and a medial side 228, the width being perpendicular to a length extending along a longitudinal axis 230 running between a toe end 232 and a heel end 234.

The sole structure 204 includes a midsole 212 that is coupled with the upper 202 along an upper surface 240 of the midsole 212 and is coupled with an outsole 214 along a lower surface of the midsole 212, which defines a bottom surface 216 of the sole structure 204. The midsole 212 defines a forefoot or first midsole portion 244 that is configured to provide a rounded portion of the bottom surface 216 within the forefoot region 220. In particular, the first midsole portion 244 defines a curved first upper surface portion 250 and a curved first lower surface portion 252, each of which curve downwardly toward the outsole 214. Each of the first upper surface portion 250 and the first lower surface portion 252 are curved along both a length and a width so that the first upper surface portion 250 is concave with respect to a first primary axis 254 that is normal to the first upper surface portion 250, and so that the first lower surface portion 252 is convex with respect to a second primary axis 256 that is normal to the first upper surface portion 250. With regard to the first lower surface portion 252, the first lower surface portion 252 is configured as a hemispherical surface that defines a radius of curvature.

With continued reference to FIGS. 7 and 8 , the outsole 214 can include a plurality of protrusions 218, e.g., lugs or spikes, that can be configured to provide increased traction. More specifically, the outsole includes a first plurality of protrusions 218 a that are dispersed along the portion of the outsole 214 that corresponds with the first midsole portion 244. The first plurality of protrusions 218 a can be equally or unequally spaced along the outsole 214 and are configured to extend outward from the outsole 214, so as to extend approximately normal to a local area of curvature on the outsole 214, e.g., to extend radially outward for a hemispherical curvature. Accordingly, the first plurality of protrusions 218 a can engage the ground when a bottom of a user's foot is angled relative to, e.g., not parallel to, the ground. Additionally, the outsole 214 can include a second plurality of protrusions 218 b that are dispersed along the heel region 224 of the outsole 214. As illustrated, the second plurality of protrusions 218 b includes four protrusions that extend downwardly and away from the midsole 212. In other embodiments, any number of protrusions can be included and configured differently, for example, to extend non-radially relative to the curvature of the outsole 214.

Furthermore, the sole structure 204 can include a stiffening member 270 that can impart the sole structure 204 with desired support and stiffness characteristics. As illustrated, the stiffening member 270 is configured as a curvilinear, fork-shaped stiffening member that is secured within a correspondingly-shaped recess formed in the upper surface 240 of the midsole 212. The stiffening member 270 includes a base 274 that extends from the heel end 234, through the heel region 224, and into the midfoot region 222 proximate the forefoot region 220. A plurality of tines 272 extend forward through the forefoot region 220 from the base 274, proximate the intersection of the forefoot region 220 with the midfoot region 122, and toward the toe end 232.

In particular, the stiffening member 270 includes four tines that are equally distributed, e.g., spaced, along the width of the forefoot region 220. More specifically, moving from the lateral side 226 to the medial side 228, the stiffening member 270 includes an outer lateral or first tine 276, an inner lateral or second tine 278, an inner medial or third tine 280, and an outer medial or fourth tine 282. The interior tines, i.e., the second tine 278 and the third tine 280, are similarly configured to one another and are disposed inward of, i.e., closer to the longitudinal axis 230, the exterior tines, i.e., the first tine 276 and the fourth tine 282, which are also similarly configured to one another, so that the first and second tines 276, 278 are mirror images of the fourth and third tines 282, 280, respectively, about the longitudinal axis 230.

Relatedly the tines 272 are configured to provide the sole structure with varying zones of flexibility and stiffness. In particular, each of the first and fourth tines 276, 282 are wider than the second and third tines 278, 280, to provide the sole structure 204 with increased stiffness and support along the respective medial and lateral peripheries of the sole structure 204, while maintaining a comparatively more flexible interior. In this way, the sole structure 204 can provide increased support when angled to contact the ground on a lateral or medial periphery, and at the same time, provide increased cushioning when the sole structure 204 contacts the ground when it is not angled with respect to the ground.

Turning now to FIGS. 9-12 , another exemplary embodiment of an article of footwear 300 is illustrated. The article of footwear 300 is similar to the article of footwear 100, in accordance with the description above, with like reference numerals referring to like features. In particular, the article of footwear 300 includes an upper 302 (see FIG. 10 ) that is coupled to and disposed above a sole structure 304, which extends between the upper 302 and the ground throughout a forefoot region 320, a midfoot region 322, and a heel region 324. That is, the article of footwear 300 has a width extending between a lateral side 326 and a medial side 328, the width being perpendicular to a length extending along a longitudinal axis 330 running between a toe end 332 and a heel end 334.

The sole structure 304 includes a midsole 312 that is coupled with the upper 302 along an upper surface 340 of the midsole 312 and is coupled with an outsole 314 along a lower surface of the midsole 312, which defines a bottom surface 316 of the sole structure 304. In the illustrated embodiment, the midsole 312 is configured as dual-density midsole having an upper or first midsole layer 312 a with a first density disposed above a lower or second midsole layer 312 b with a second density, which can be co-molded or coupled together by an adhesive. The first midsole layer 312 a and the second midsole layer 312 b can have the same or different densities to provide the desired cushioning characteristics. Likewise, the relative thicknesses of the first midsole layer 312 a and the second midsole layer 312 b can be varied to achieve the desired balance of support and cushioning.

In addition, the midsole 312 is configured to have a rounded lower surface and defines a rounded first midsole portion 344 disposed within the forefoot region 320 and a rounded second midsole portion 346 disposed within the heel region 324. The first midsole portion 344 can define a first upper surface portion 350 and a first lower surface portion 352. The second midsole portion 346 can define a second upper surface portion 358 and a second lower surface portion 360.

With reference to FIG. 11 , in particular, each of the first lower surface portion 352 and the second lower surface portion 360 are curved downward toward the outsole 314 along their respective widths and lengths. Accordingly, the first lower surface portion 352 can define a first curvature 352 a along its width and a second curvature 352 b along its length, and the second lower surface portion 360 can define a third curvature 360 a along its width and a second curvature 360 b along its length. The respective curvatures of the first and second lower surface portions 352, 360 can be configured so that the first and second lower surface portions 352, 360 have an ellipsoidal outer profile. In other embodiments, the curvatures of the first and second lower surface portions 352, 360 can be configured differently to achieve different outer profiles of the first and second lower surface portions 352, 360.

With reference to FIGS. 10 and 12 , the sole structure 304 further includes a fork-shaped stiffening member 370. The stiffening member 370 is similar to the stiffening member 170, in that it includes a plurality of tines 372, i.e., three, extending from a base 374 in a heel-to-toe direction. However, the base 374 of the stiffening member 370 extends from the heel end 334, through the heel region 324 and the midfoot region 322, to the intersection between the midfoot region 322 and the forefoot region 320. Additionally, because the midsole 312 is a dual layer midsole, the stiffening member 370 is disposed internally to the midsole 312 so that it is between the first midsole layer 312 a and the second midsole layer 312 b. More specifically, the stiffening member 370 is received within a corresponding recess of the first midsole layer 312 a. In other embodiments, the stiffening member 370 may be received within a corresponding recess of the second midsole layer 312 b, or, alternatively, within recesses in both of the layers 312 a and 312 b.

Turning to FIG. 13 , another sole structure 404 for an article of footwear is illustrated. The sole structure 404 is similar to the sole structure 304, but includes discrete midsole portions that are spaced apart from one another. More precisely, the sole structure 404 includes a midsole 412 that is coupled to an outsole 414, wherein the midsole 412 is comprised of a first midsole portion 444 disposed within a forefoot region 420 and a second midsole portion 446 disposed within a heel region 424. The first midsole portion 444 and the second midsole portion 446 are spaced apart about a midfoot region 422. Additionally, the outsole 414 only includes a single outsole portion that is shaped to couple with the first midsole portion 444.

To secure the first midsole portion 444 and the second midsole portion 446 in the aforementioned spaced relationship, each of the first midsole portion 444 and the second midsole portion 446 are secured to a fork-shaped stiffening member 470 with a plurality of tines 472 extending toward a toe end 432 from a base that extends between the heel end 434 to the intersection of the midfoot region 422 with the forefoot region 420. In particular, the tines 472 are embedded in the first midsole portion 444, while the second midsole portion 446 is secured below the base 474 in the heel region 424, leaving the base 474 exposed within both the heel region 424 and the midfoot region 422. In this way, the stiffening member 470 bridges a gap 477 between the first midsole portion 444 and the second midsole portion 446, to fixedly secure the first midsole portion 444 and the second midsole portion 446 relative to one another. Accordingly, the first midsole portion 44 and the second midsole portion 446 are in a fixed spatial relationship and at least a portion of the midfoot region 422 can consist only of the stiffening member 470. However, in some cases, the outsole 414 may also extend across the gap 477, as may provide protection to the stiffening member 470. Correspondingly, at least a portion of the midfoot region 422 may consist only of the stiffening member 470 and the outsole 414, and the outsole 414 may or may not be coupled to the stiffening plate 470.

Any of the embodiments described herein may be modified to include any of the structures or methodologies disclosed in connection with different embodiments. For example, certain features and combinations of features that are presented with respect to particular embodiments in the discussion above can be utilized in other embodiments and in other combinations, as appropriate. Similarly, materials or construction techniques, other than those disclosed above, may be substituted or added in some embodiments according to known approaches. Further, the present disclosure is not limited to articles of footwear of the type specifically shown. Still further, aspects of the articles of footwear of any of the embodiments disclosed herein may be modified to work with any type of footwear, apparel, or other athletic equipment.

As noted previously, it will be appreciated by those skilled in the art that while the disclosure has been described above in connection with particular embodiments and examples, the disclosure is not necessarily so limited, and that numerous other embodiments, examples, uses, modifications and departures from the embodiments, examples and uses are intended to be encompassed by the claims attached hereto.

INDUSTRIAL APPLICABILITY

Numerous modifications to the present invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as illustrative only and is presented for the purpose of enabling those skilled in the art to make and use the invention. The exclusive rights to all modifications which come within the scope of the appended claims are reserved. 

We claim:
 1. A sole structure for an article of footwear having an upper, the sole structure comprising a midsole that is coupled to the upper along an upper surface of the midsole and to an outsole along a lower surface that is opposite the upper surface, both the upper surface and the lower surface being curved along a width of the sole structure to curve away from the upper and toward the outsole within a forefoot region; and a stiffening member coupled to the midsole and extending from a heel end toward a toe end, the stiffening member including a base disposed within at least a midfoot region and a plurality of tines extending into the forefoot region from the base.
 2. The sole structure of claim 1, wherein, along the width of the sole structure, the upper surface defines a first curvature and the lower surface defines a second curvature.
 3. The sole structure of claim 2, wherein the first curvature is different from the second curvature so that the midsole has a crescent-like cross-sectional shape taken perpendicular to a longitudinal axis of the sole structure.
 4. The sole structure of claim 2, wherein the first curvature defines a first radius of curvature and the second curvature defines a second radius of curvature that is smaller than the first radius of curvature.
 5. The sole structure of claim 1, wherein the lower surface is curved to have an ellipsoidal shape in the forefoot region.
 6. The sole structure of claim 5, wherein the ellipsoidal shape is a hemispherical shape.
 7. The sole structure of claim 5, further comprising a plurality of ground engaging elements extending radially outward from the lower surface in the forefoot region.
 8. The sole structure of claim 1, wherein the midsole includes a first midsole portion that is disposed in the forefoot region and a second midsole portion that is disposed in a heel region of the sole structure.
 9. The sole structure of claim 8, wherein the first midsole portion and the second midsole portion are spaced apart from one another by a gap in the midfoot region.
 10. The sole structure of claim 9, wherein the stiffening member bridges the gap between the first midsole portion and the second midsole portion.
 11. The sole structure of claim 1, wherein the plurality of tines includes a first tine extending along a lateral side of the sole structure and a second tine extending along a medial side of the sole structure.
 12. The sole structure of claim 11, wherein the plurality of tines further includes a third tine that is positioned between the first tine and the second tine, the third tine extending along a longitudinal axis of the sole structure.
 13. The sole structure of claim 1, wherein the base of the stiffening member extends into a heel region of the sole structure.
 14. The sole structure of claim 1, wherein the plurality of tines are disposed within the midsole in the forefoot region.
 15. The sole structure of claim 14, wherein the midsole includes an upper midsole layer defining the upper surface and a lower midsole layer defining the lower surface, and wherein the plurality of tines are disposed between the upper midsole layer and the lower midsole layer.
 16. The sole structure of claim 15, wherein the base of the stiffening member extends along the upper surface in the midfoot region.
 17. A sole structure for an article of footwear having an upper, the sole structure comprising: a midsole defining an upper surface configured to couple to the upper and a lower surface opposite the upper surface, the lower surface being curved in a forefoot region of the sole structure so that the lower surface has an ellipsoidal shape; and a stiffening member having a plurality of tines that extend from a base, the plurality of tines extending in a heel-to-toe direction within the forefoot region and including at least a first tine extending along a first curvature along a lateral side of the midsole to provide the lateral side of the midsole with a first stiffness and a second tine extending along a second curvature along a medial side of the midsole to provide the medial side of the midsole with a second stiffness.
 18. The sole structure of claim 17, wherein the midsole has a crescent-like cross-sectional shape taken perpendicular to a longitudinal axis of the sole structure, such that the midsole is thickest proximate the longitudinal axis and gradually thins moving outward toward each of a medial side and a lateral side of the sole structure.
 19. The sole structure of claim 18, further comprising an outsole that is coupled to the lower surface of the midsole to provide a ground engaging surface, the outsole conforming with the shape of the lower surface.
 20. A sole structure for an article of footwear having an upper, the sole structure comprising: a midsole that is configured to couple to the upper along an upper surface of the midsole and to an outsole along a lower surface that is opposite the upper surface, the lower surface being curved along both of a width and a length of the sole structure to form a continuously rounded and convex surface that extends throughout a forefoot region of the sole structure, and a stiffening member coupled to the midsole, the stiffening member having a plurality of tines that extend from a base, the plurality of tines extending in a heel-to-toe direction within the forefoot region and including at least a first tine extending along a first curvature along a lateral side of the midsole to provide the lateral side of the midsole with a first stiffness and a second tine extending along a second curvature along a medial side of the midsole to provide the medial side of the midsole with a second stiffness. 